ACOG Releases Report on Dystocia and Augmentation of Labor

The American College of Obstetricians and Gynecologists (ACOG) recently published a clinical practice guideline on dystocia and augmentation of labor. The complete guideline, ACOG Practice Bulletin no. 49, appeared in the December 2003 issue of Obstetrics and Gynecology. The report provides a review of the definition of dystocia, the risk factors associated with dystocia, the criteria that require delivery, and the approaches to clinical management of labor complicated by dystocia. It focuses on labor subsequent to entering the active phase, diagnosis of active-phase abnormalities, clinical considerations, and management recommendations for the active phase and the second stage of labor.

Dystocia is characterized by the slow and abnormal progression of labor and is the leading indication for primary cesarean delivery in the United States. Because dystocia rarely can be diagnosed with certainty, the imprecise term “failure to progress” has been used, which includes lack of progressive cervical dilation or lack of descent of the fetal head, or both. Dystocia should not be diagnosed until an adequate trial of labor has been achieved. According to ACOG, a more practical classification is to categorize labor abnormalities as slower-than-normal (protraction disorders) or complete cessation of progress (arrest disorders).

In the report, ACOG lists parameters for defining when labor becomes prolonged and intervention should be considered. In nulliparous women, the diagnosis should be considered when the second stage of labor exceeds two hours without regional anesthesia and three hours if anesthesia was used. In multiparous women, the time limit is one hour without anesthesia and two hours if it was administered. A prolonged second stage of labor warrants clinical reassessment of the patient, fetus, and expulsive forces.

According to ACOG, risk factors for dystocia include epidural analgesia, occiput posterior position, longer first stage of labor, nulliparity, short maternal stature, birth weight, and high station at complete cervical dilation. Chorioamnionitis, pelvic contractions, and macrosomia also may affect the progression of labor.

Recommendations

The guideline includes the following clinical considerations and recommendations:

• Dystocia cannot be predicted with certainty. According to ACOG, risk factors (see accompanying table) for difficult delivery in nulliparous women in the second stage of labor include short stature (less than 5 ft [150 cm]), age greater than 35 years, gestational age greater than 41 weeks, interval between epidural induction and full cervical dilation for more than than six hours, fetal station above +2 cm at full cervical dilation, or occiput posterior fetal position.

• Epidural anesthesia is associated with increases in duration of the first and second stages of labor, incidence of fetal malpositions, use of oxytocin, and operative vaginal delivery. Epidural anesthesia was not shown to increase the cesarean delivery rate for dystocia.

• No evidence supports routine use of intrauterine pressure catheters for labor management. They may be beneficial when the evaluation of contractions is difficult because of obesity, there is a lack of one-on-one nursing care, or response to oxytocin is limited.

• Walking during labor has not been shown to enhance or impair progress in labor. It is not harmful, and mobility may result in greater comfort and ability to tolerate labor.

• Not enough evidence is available to support the use of x-ray pelvimetry in patients whose fetuses have cephalic presentations. Additional prospective studies are necessary to establish the usefulness of this diagnostic modality to predict dystocia, so it is not recommended at this time.

• Continuous support during labor from caregivers (nurses, midwives, or lay persons) has several benefits to the patients and newborns without any evidence of harmful effects.

• Active management of labor is not associated with unfavorable maternal or neonatal outcomes. It may lead to shortened labor in nulliparous women, but it has not led to a consistent reduction in cesarean deliveries.

• Current data do not support the theory that low-dose oxytocin regimens are superior to high-dose regimens for augmentation of labor. Low-dose regimens are associated with less uterine hyperstimulation and lower maximum doses. High-dose regimens may be used for multiparous women, but no data support the use of high-dose oxytocin regimens for augmentation in a patient with a previously scarred uterus.

• Twin gestation does not preclude the use of oxytocin for labor augmentation. Augmentation is not a significant risk factor for cesarean delivery or adverse outcomes.

• Amniotomy may enhance progress in the active phase and negate the need for oxytocin augmentation, but it may increase the risk of chorioamnionitis.

• No definitive evidence has identified the most effective method of fetal heart rate surveillance when oxytocin is used for augmentation. Intermittent auscultation is equivalent to continuous electronic fetal monitoring when performed at specific intervals with a one-to-one nurse-to-patient ratio. No data indicate the optimal frequency for intermittent auscultation in the absence of risk factors.